1. Field of the Invention
The present invention relates to a method of and a device for moving picture decoding.
2. Description of the Related Art
In a moving picture decoding device, a decoding process is carried out in the order of coded data which is provided, and the data is stored in a frame memory, wherein the decoded picture data is read out of the frame memory in the order of original pictures. The read data is processed in compliance with display parameters and converted into analog video signals.
The display parameters are as follows;
in picture display extension, three sets of frame center offsets (horizontal and vertical offsets),
in picture spatial scalable extension,
spatial temporal weight code table index for up sample;
lower layer vertical offset;
lower layer horizontal offset;
lower layer temporal reference; and
lower layer interlaced field select;
repeat first field; and
top field first.
In FIG. 5, I, B and P respectively indicate I-picture, B-picture and P-picture, and numbers attached to the I, B, and P show a sequence of decoding process.
The display parameters are separated by a variable length decoding circuit and are used in a display circuit. After use, the contents thereof are released. For example, in FIG. 5, while a decoding process of I1, B2, B3 and P4 is sequentially performed, the display parameters are separated by the variable length decoding circuit for every picture and are stored in the respective register groups 1 to 4. The contents thereof are released when a data process in the display circuit is finished as to corresponding picture, and they can be overwritten. The hatched sections in FIG. 5 are released periods. Next, while a decoding process of B5, B6 and P7 is carried out in order, the display parameters are separated for every picture by the variable length decoding circuit, and each of them is stored in register groups 2, 3 and 1 in the order of release.
Since in a prior art moving picture decoding device four sets of register groups were required in order to hold display parameters, this caused enlargement of the circuit configuration. Furthermore, in storing and reading the display parameters, since it was necessary to properly select one of the four register groups, the control was complicated.
In view of above problems, it is an object of the present invention to provide a method of and a device for moving picture decoding which are able to reduce the configuration of a display parameter synchronous holding circuit and to simplify its control operation.
In the 1st aspect of the present invention, there is provided a moving picture decoding device which separates display parameters and a picture coding type from coded data, decodes the coded data, stores the separated display parameters, reads the stored display parameters in the order of display pictures, and processes decoded data according to the read display parameters, the decoding device comprising: a first, a second and a third register groups; and a control circuit for storing a content of the first register group into the second register group and storing the separated display parameters into the first register group when the picture coding type indicates a reference picture, and for storing the separated display parameters into the second register group when the picture coding type indicates a non-reference picture; wherein a content of the second register group is stored as display parameters in the order of the display pictures into the third register group in synchronization with a display synchronization signal.
With the 1st aspect of the present invention, since only three sets of register groups are enough, the circuit configuration can be reduced in comparison with a prior art where four sets are provided. Furthermore, since storing control is carried out with respect to the 1st register group or the 2nd register group in compliance with picture coding type, an effect of simplifying the control can be obtained. Still furthermore, since it is essential only that the output of the 2nd register group is stored in the 3rd register group in synchronization with the display synchronization signal and decoded data is processed in compliance with the output of the 3rd register group, it is not necessary to select one set from a plurality of sets of register groups, therefore data reading control from register groups can be simplified.
In the 2nd aspect of the present invention, there is provided a moving picture decoding device which separates display parameters and a picture coding type from coded data, decodes the coded data, stores the separated display parameters, reads the stored display parameters in the order of display pictures, and processes decoded data according to the read display parameters, the decoding device comprising: a first register group for receiving the separated display parameters, and for storing the separated display parameters in response to a first latch signal; a selecting circuit for outputting either the separated display parameters or an output of the first register group in compliance with a selection controlling signal; a second register group for receiving an output of the selecting circuit, and for storing the output of the selecting circuit in response to a second latch signal; a third register group for receiving an output of the second register group, and for storing the output of the second register group in response to a display synchronization signal; and a control circuit for outputting the selection controlling signal to select the output of the first register group, outputting the second latch signal with being activated and outputting the first latch signal with being activated when the picture coding type indicates a reference picture, and for outputting the selection controlling signal to select the separated display parameters, outputting the second latch signal with being activated when the picture coding type indicates a non-reference picture.
In the 3rd aspect of the present invention, there is provided a moving picture decoding device as defined in the 2nd aspect, wherein the control circuit comprises: a judging circuit for judging whether the picture coding type indicates the reference picture or the non-reference picture; and a control signal generating circuit for generating the selection controlling signal, the first latch signal and the second latch signal in compliance with judgement result of the judging circuit.
In the 4th aspect of the present invention, there is provided a moving picture decoding device according to in the 3rd aspect, wherein the judging circuit outputs a first pulse when the picture coding type indicates the reference picture, and outputs a second pulse when the picture coding type indicates the non-reference picture, and wherein the control signal generating circuit outputs the first pulse as the selection controlling signal, outputs a delayed signal of the first pulse as the first latch signal, and outputs a signal corresponding to a logical add of the first pulse and the second pulse as the second latch signal.
In the 5th aspect of the present invention, there is provided a moving picture decoding device as defined in the 1st aspect, wherein the display synchronization signal is a vertical synchronization signal.
In the 6th aspect of the present invention, there is provided a moving picture reproducing device including a moving picture decoding device, the decoding device separates display parameters and a picture coding type from coded data, decodes the coded data, stores the separated display parameters, reads the stored display parameters in the order of display pictures, and processes decoded data according to the read display parameters, the decoding device comprising: a first, a second and a third register groups; and a control circuit for storing a content of the first register group into the second register group and storing the separated display parameters into the first register group when the picture coding type indicates a reference picture, and for storing the separated display parameters into the second register group when the picture coding type indicates a non-reference picture; wherein a content of the second register group is stored as display parameters in the order of the display pictures into the third register group in synchronization with a display synchronization signal.
In the 7th aspect of the present invention, there is provided a moving picture decoding method which separates display parameters and a picture coding type from coded data, decodes the coded data, stores the separated display parameters, reads the stored display parameters in the order of display pictures, and processes decoded data according to the read display parameters, the method comprising the steps of: preparing a first, a second, and a third register groups; control circuit for outputting the selection controlling signal to select the output of the first register group, outputting the second latch signal with being activated and outputting the first latch signal with being activated when the picture coding type indicates a reference picture, and for outputting the selection controlling signal to select the separated display parameters, outputting the second latch signal with being activated when the picture coding type indicates a non-reference picture.
Other aspects, objects, and the advantages of the present invention will become apparent from the following detailed description taken in connection with the accompanying drawings.